1. Field of the Invention
The present invention relates to a data transmission device, a reception device, a data transmission system, and a data transmission method which are used when a plurality of program data are transmitted by using, e.g., a digital satellite broadcast.
2. Description of the Related Art
At present, a digital satellite broadcast which transmits digital data by using a communication satellite to perform broadcast has spread. In this digital satellite broadcast, video and audio signals are compressed and encoded by a predetermined scheme, and the compressed and encoded video and audio signals are transmitted to viewers through the communication satellite. As a compressing/coding scheme for video and audio signals, for example, MPEG2 (Moving Picture Experts Group) is used.
FIG. 10 shows the outline of a typical digital broadcast system. The program transmission side is constituted by an up-link station, a program provider, and a management system.
Video/audio data from a program provider 101 is supplied to an encoder, multiplexer 103 of MPEG (Moving Pictures Expert Group)2 of an up-link station 102. The video/audio data is compressed in the MPEG2 encoder, multiplexer 103, and the compressed video/audio data is filled in a packet having a length of 188 bytes. A plurality of programs and packets of video/audio data corresponding to the programs are multiplexed to form a transport packet of MPEG2. A large number of transport packets are connected to each other to form a transport stream. The number of transport streams corresponds to the number of transponders mounted on a communication satellite.
The MPEG2 transport packets are supplied to a transmission system 104. In the transmission system 104, processes such as a scramble process for each packet, error correction coding for each packet, and modulation are performed, and a modulated output is supplied to a transmission antenna 105. The scramble process is required to realize conditional access used to control the audiovisual quality for each viewer. For example, a pay-per view contract in which only a certain program is watched every paying is made possible. A key for canceling the scramble is supplied from a key management system 106 to the MPEG2 encoder, multiplexer 103, and is inserted into the transport packet as one of packets like video/audio information.
The MPEG2 packets are integrally managed by a program management system 107. The program management system 107 is coupled to the key management system 106 to decode a key for canceling scramble. A client management system 108 is arranged to manage items or the like related to audiovisual contracts. Accounting information is transmitted between the client management system 108 and the house of a viewer through a telephone line 109.
Broadcast radio wave is transmitted from the transmission antenna 105 and received by a reception antenna 111 of each house through a communication satellite 110. A receiver 112 is connected to the reception antenna 111. The receiver 112 is constituted by a tuner for designating a reception transponder, a demodulator, a scramble unit for canceling scramble, a demultiplexer for designating separate packets, a video decoder, an audio decoder, and the like. Decoded video/audio signals are supplied to a television receiver 113.
A key for canceling scramble is encoded and transmitted as relevant information together with image/voice. The key for solving cryptography is stored in an IC card 114 inserted in the receiver 112. Program scrambles which can be solved by a transmission side can be controlled by the transmission side on the basis of the contract information of each reception system. A receiver having a conditional access function is called an IRD (Integrated Receiver/Decoder).
The above digital satellite broadcast system has only just begun to be practically used, and a program for controlling a recent receiver on a reception side may be variably changed. For this reason, this program is stored as data in a programmable ROM built in the receiver. As the programmable ROM, a flash ROM such as an EEPROM (Electrically Erasable Programmable ROM) is known. This change generally has an object to provide new services and additional values to clients. Several methods can be effective as countermeasures against the change in program.
For example, when a program ROM built in a receiver is replaced with another one, or the receiver is entirely replaced with another one, a countermeasure against the change in program can be made. When an IC card in which a new program is stored is distributed to a client by using the interface, for an IC card, arranged in the receiver, the new program can be loaded from the IC card. However, when a large number of receivers which have been arranged, it is difficult to replace the ROMs of the receivers and collect the receivers. In addition, a method of distributing IC cards requires high cost. Since each IC card has a relatively small memory capacity, the IC card cannot easily store a program.
As a method of solving the above problem, the following method is provided. That is, latest program information is received from a transmission side, and this program is loaded on a receiver on a reception side. More specifically, program data is inserted into a data stream transmitted by satellite broadcast using, e.g., the MPEG2 system, and the program data is received by a viewer by means of a receiver to download the program data. The downloaded program data is temporarily written in, e.g., a RAM built in the receiver, and the program data is transferred from the RAM to a flash ROM, thereby updating the program.
A piece of software of one type is conventionally applied to all reception devices. More specifically, a necessary piece of software cannot be selected from pieces of software of various types. For this reason, on the receiver side, the type of a host processor (CPU) or an OS (Operation System), the type of an interpreter for executing a program, or the like must be limited to one. Therefore, program data cannot be downloaded on a receiver in which these types are not integrated.
For example, in a personal computer or the like, when a program is to be downloaded, an operator examines the version of the program, and the version can be compared with the version of the same program owned by the operator at present. In this manner, in a personal computer or the like, the programs whose versions are equal to each other can be prevented from being repetitively downloaded.
However, downloading by such a conventional receiver for satellite broadcast is performed regardless of the version of a program to be downloaded. Therefore, it is a problem that a program whose version is equal to the version of the program which has been downloaded may be repetitively downloaded in vain. It is another problem that the version of the downloaded program may be older than the version of the program which is owned.
Also in downloading by a personal computer, determination of version information is left to an operator""s hand. For this reason, the failure described above may occur in the downloading.
In addition, program data to be downloaded has a size of, e.g., several MBytes. Therefore, the downloading of the program data requires several minutes or several ten minutes. In a conventional system, a progress state of downloading, e.g., the rate of the size of downloaded data to the total size of program data is not displayed. For this reason, the following problem arises. That is, time of the end of downloading cannot be recognized, and an operator who executes the downloading is displeasured.
On the other hand, when a different types of program data are to be transmitted, the following method may be used. That is, a plurality of transmission paths are used, and these program data are transmitted through different paths, respectively. For example, in this satellite broadcast, a plurality of transponders to which different carrier frequencies are allocated are used, so that data streams are transmitted to receivers. Therefore, transponders can be allocated to receivers depending on the makers and models of the receivers. However, a conventional system has no information representing a transponder from which specific program data is transmitted. For this reason, corresponding program data cannot be substantially downloaded on the reception side.
Therefore, it is an object of the present invention to provide a data transmission device, a reception device, a data transmission system, and a data transmission method which can select proper data from a plurality of data which are multiplexed and transmitted to download the selected proper data.
In order to solve the above problem, the present invention provides a data transmission device for time-divisionally multiplexing signals of a plurality of channels and further multiplexing the plurality of time-divisionally multiplexed signals to simultaneously transmit the signals, characterized in that receiver maker identification information for identifying makers of reception devices for receiving transmitted information and receiver model identification information for identifying models of the makers of the reception devices are transmitted.
In order to solve the above problem, the present invention provides a data reception device for designating a predetermined signal from multiplexed and transmitted signals to receive the predetermined signal, characterized by comprising: means for extracting only necessary information on the basis of receiver maker identification information and receiver model identification information included in the received signal to store the extracted information; and control means for using the stored information as a program for unit control.
In order to solve the above problem, the present invention provides a data transmission system for time-divisionally multiplexing signals of a plurality of channels and further multiplexing the plurality of time-divisionally multiplexed signals to simultaneously transmit the signals, and designating a predetermined signal from the multiplexed and transmitted signals to receive the predetermined signal, characterized by comprising: transmission means for transmitting receiver maker identification information for identifying makers of reception devices for receiving transmitted information and receiver model identification information for identifying models of the makers of the reception devices; reception means for receiving the transmitted information; means for extracting only necessary information on the basis of the receiver maker identification information and the receiver model identification information included in the received information to store the extracted information; and control means for using the stored information as a program for unit control.
In order to solve the above problem, the present invention provides a data transmission method for time-divisionally multiplexing signals of a plurality of channels and further multiplexing the plurality of time-divisionally multiplexed signals to simultaneously transmit the signals, characterized in that receiver maker identification information for identifying makers of reception devices for receiving transmitted information and receiver model identification information for identifying models of the makers of the reception devices are transmitted.
As described above, according to the present invention, since receiver maker identification information for identifying makers of reception devices for receiving transmitted information and receiver model identification information for identifying models of the makers of the reception devices are transmitted, proper information can be selected from pieces of multiplexed and transmitted information to receive the proper information.